devmem2 command can't update REG value from user space

[zhaolj]

I am using IMX8M EVK board and run Ubuntu. I use devmem command to debug , but I found that there are issue on IMX8M which i canit update REG value but on IMX6 everything is OK. I wonder if there some restrict condition in ARMV8 such EL0/EL1,  pls help me on this.

Can't update SOC REG value :(REG is RW type)

./devmem2 0x3d400100 w 0x1a201b00

/dev/mem opened.

Memory mapped at address 0xffffb45cc0000 value at address 0x3d400100(0xffffb45cc0000):0x1A201B22

Written 0x1A201B00; readback 0x1A201B22

[igorpadykov]

Hi Zhao

one can try with memtool and NXP Demo Image

https://source.codeaurora.org/external/imx/imx-test/tree/test/memtool?h=lf-5.10.y_1.0.0

​i.MX 8M Quad EVK​

Best regards
igor

[zhaolj]

Thanks for your reply. I have try your suggestion but still can't modify REG value.
Just guess: this issue may be some kernel configuration not allow modify REG from user space

memtool DDRC.DRAMTMG0.WR2PRE
DDRC Addr:0x3d400000
DDRC.DRAMTMG0 Addr:0x3D400100 Value:0x1A201B22 -
DDRC.DRAMTMG0.WR2PRE(24..30) :0x1a
DDRC.DRAMTMG0_SHADOW Addr:0x3D402100 Value:0x0B070A07 -
DDRC.DRAMTMG0_SHADOW.WR2PRE(24..30) :0xb

memtool DDRC.DRAMTMG0.WR2PRE=0x8
write 0x00000008 to Bit 24..30 of 0x3D400100

memtool DDRC.DRAMTMG0.WR2PRE
DDRC Addr:0x3d400000
DDRC.DRAMTMG0 Addr:0x3D400100 Value:0x1A201B22 -
DDRC.DRAMTMG0.WR2PRE(24..30) :0x1a
DDRC.DRAMTMG0_SHADOW Addr:0x3D402100 Value:0x0B070A07 -
DDRC.DRAMTMG0_SHADOW.WR2PRE(24..30) :0xb